Community therapists rarely use interventions with empirical support and prior attempts to disseminate empirically supported behavioral treatments (ESBTs) to community settings have not been based on understanding key ingredients of the therapeutic process, without which community therapists may be inadequately trained. Principle-based training that uses active learning strategies and incorporates feedback about fidelity holds promise for application and sustainability of ESBTs in community settings. Pediatric OCD has a clear theory underlying treatment (Exposure and Response Prevention) and is an ideal disorder with which to test an improved training model linking theory, in-session therapist behavior, and patient outcome. The first phase (R21) of this project will use a theory-derived observational coding system to examine therapist behavior during treatment for a sample of children (N = 160) who received CBT as part of three multisite treatment trials for pediatric OCD (POTS). Specifically, we will look for evidence that prescribed and proscribed therapist behaviors during treatment are related to theoretical mechanism of change (habituation) and to patient treatment outcome. We will also validate a short fidelity rating system that measures prescribed and proscribed therapist behaviors, in preparation for providing feedback about those behaviors to therapists in community settings. The second phase (R33) will use R21 data to develop and pilot a randomized trial of two delivery formats of theory-based CBT training for community providers treating pediatric OCD. Therapists (N = 16) across two community sites will be randomized to receive a workshop plus weekly supervision or a workshop plus telephone consultation service. All therapists will receive regular feedback about prescribed and proscribed behaviors identified in the R21 phase using the fidelity rating system. We will measure therapist-level outcomes (e.g., knowledge, proficiency, satisfaction) and patient-level outcomes (e.g., symptoms, disability, service utilization, satisfaction) for purposes of assessing feasibility and acceptability of training and related treatment and in preparation for R01 trial. Results from this study will inform development of future theory-based training programs for therapists as well as teaching use of exposure as a tool for other anxiety disorders.